Revert "remove class based exercises"

This reverts commit 290e7f1da4.

timer/timer.spec.js

@@ -0,0 +1,35 @@
+var Timer = require ('./timer.js');
+
+describe('Timer', function() {
+	var timer; // undefined, here for scope purposes
+
+	beforeEach(function () {
+		timer = new Timer.timeFormat();
+	});
+
+	it('should initialize to 0 seconds', function() {
+		expect(timer.seconds).toEqual(0); // makes sure timer starts with 0 seconds
+	});
+	
+	describe('time_string', function() {
+		it('should display 0 seconds as 00:00:00', function() {
+			timer.seconds = 0;
+			expect(timer.time_string()).toEqual("00:00:00");
+		});
+
+		it('should display 12 seconds as 00:00:12', function() {
+			timer.seconds = 12;
+			expect(timer.time_string()).toEqual("00:00:12");
+		});
+
+		it('should display 66 seconds as 00:01:06', function() {
+			timer.seconds = 66;
+			expect(timer.time_string()).toEqual("00:01:06");
+		});
+
+		it('should display 4000 seconds as 01:06:40', function() {
+			timer.seconds = 4000;
+			expect(timer.time_string()).toEqual("01:06:40");
+		});
+	});
+});